1. Field of the Invention
The present invention relates to a control method and system for a motor, more particularly, to a control method and system using a micro-programming & memory controller for a motor.
2. Description of the Related Art
FIG. 1 shows a conventional PI-PWM (Proportion Integration-Pulse Width Modulation) current control system 11 for a motor 10. The conventional PI-PWM current control system 11 comprises: a first difference operator 12, a PI controller 14, a second difference operator 15, a PWM comparator 16 and an inverter 18. The control system 11 receives three phase reference currents 20 to the first difference operator 12, and detects three phase actual currents 22 from a motor 10. The first difference operator 12 calculates three phase difference currents between the three phase reference currents 20 and three phase actual currents 22.
The three phase difference currents are amplified by the PI controller 14 to obtain three phase control voltages. The second difference operator 15 calculates difference voltages between the three phase control voltages and three phase triangle-wave signals 24. The PWM comparator 16 receives the three phase difference voltages and outputs three phase switch signals to the inverter 18. According to the three phase switch signals, the inverter 18 outputs three phase input voltages to the motor 10 and controls the motor 10.
However, the conventional PI-PWM current control system 11 has the current phase-lag problem. Referring to FIGS. 2A, 2B, 3A, 3B and 3C, they show the comparison between the three phase actual currents and the three phase reference currents, according to the conventional PI-PWM current control system. FIG. 2A shows A phase reference current Ia1, refer. FIG. 2B shows A phase actual current Ia1,actual. FIG. 3A shows a comparison between A phase reference current Ia1,refer and A phase actual current Ia1,actual. FIG. 3B shows a comparison between B phase reference current Ib1,refer and B phase actual current Ib1,actual. FIG. 3C shows a comparison between C phase reference current Ic1,refer and C phase actual current Ic1,actual. As shown in FIGS. 2A, 2B, 3A, 3B and 3C, the current phase-lag problem exists between the three phase reference currents Ia1,refer, Ib1,refer, Ic1,refer and three phase actual currents Ia1,actual, Ib1,actual, Ic1,actual.
Besides, when a software is utilized to perform the operation of the PI controller 14, the conventional PI-PWM current control system 11 has the high noise problem. FIGS. 4A, 4B, 5A, 5B and 5C show the comparison between the three phase actual currents and the three phase reference currents, according to the conventional PI-PWM current control system 11 using a software to perform the PI controller 14. FIG. 4A shows A phase reference current Ia2, refer, FIG. 4B shows A phase actual current Ia2,actual, FIG. 5A shows a comparison between A phase reference current Ia2,refer and A phase actual current Ia2,actual, FIG. 5B shows a comparison between B phase reference current Ib2,refer and B phase actual current Ib2,actual, FIG. 5C shows a comparison between C phase reference current Ic2,refer and C phase actual current Ic2,actual. As shown in FIGS. 4A, 4B, 5A, 5B and 5C, the three phase actual currents Ia1,actual, Ib1,actual, Ic1,actual have the high noise problem.
Therefore, it is necessary to provide an innovative and progressive control method and system to solve the above problem.